1938 · the hereditary Honinbo's last game
Shusai's sealed move 121 closes a retirement game and an era
When Minoru Kitani put Black 121 into an envelope, sealed moves entered a major Japanese title game. A fairer clock also became a weapon, and Yasunari Kawabata turned the collision into The Master of Go.
Minoru Kitani (Black) vs Honinbo Shusai Meijin (White) · 1938.06.26—12.04 · fourteen adjournments · Black won by 5 · no komi
Why one game lasted half a year
Shusai was the twenty-first and last hereditary Honinbo. Earlier custom let the player to move, often Shusai, adjourn without revealing the next move. The new sealed-move rule required that move to be written secretly and opened only at resumption, making outside study time more symmetrical.
Illness produced a suspension of roughly three months. Newspaper reporter Yasunari Kawabata covered the match and later transformed it into The Master of Go. The SGF, reportage, and novel are three different kinds of evidence and should not be merged.
Why Black 121 caused an argument beyond the board
Kitani spent one hour forty-four minutes on the sealed Black 121. It stood away from the visible fight and made it hard for White to know which region to study during the break.
Modern competition treats that uncertainty as the point of sealing. To Shusai, experiencing the rule for the first time, it felt as if a younger rival had turned reform into a tactical instrument.
Move 121 writes several debts instead of cashing one
The move does not capture immediately. It links distant weaknesses, initiative, and central potential, so that every later local decision changes another region's balance.
That delayed value is why the TreeView starts after White 120: it tests a global pivot against candidates that realize local value sooner.
AI cannot judge the envelope, only the Go inside it
The red branch preserves Kitani's H16 and adds a precomputed continuation. Other branches come from the same 10,000-visit root; a candidate identical to the played move is shown only once, and history is never rewritten to match AI.
Read win rate, score lead, and visits together. They measure winning probability, board value, and search attention, not one interchangeable ranking.
What the three playable routes compete for
H16 leaves Black near 98.7%, moving the lead only from +4.4 to +4.6: enormous controversy, little numerical disturbance.
O8 works through the center-right with O8, R6, N11, and M11.
K2 begins on the lower side before turning to E19, reversing the order of the two wings.
The envelope held a changing idea of fairness
Kitani won by five, but move 121 did not single-handedly win six months of Go. Its importance comes from board value, rules, and generational ethics colliding at one point.
Use the TreeView to judge it as Go first, then return to 1938 to understand why a rule now considered fair could still wound the old order's final master.